A brazed heat exchanger, which is a condenser that forms one component of an air-conditioning system and cyclically condenses a circulating refrigerant, e.g. by means of a cooling air flow, is known from European Patent Publication EP 1 147 930 B1 and from numerous other publications.
Brazing is usually carried out in a brazing furnace, into which the heat exchanger described at the outset is introduced after appropriate preassembly and pretreatment and is generally produced in a single brazing operation. This means that all the connections are brazed in a single brazing operation.
There are often problems with brazing. The causes thereof are many and various and are often difficult to determine. They can be roughly divided into causes of a procedural kind and those of a product-specific kind and, where applicable, those which represent a mixture of the two kinds.
In respect of the product (heat exchanger) described at the outset, causes of a product-specific kind will be explored only briefly here. These include material-related and design-related causes, e.g. impermissible air gaps or the like.
One specific cause of a product-specific kind sometimes resides in the fact that the above-denoted components of the brazed heat exchanger have different masses, for which reason it is not possible to bring all the components simultaneously to the brazing temperature. For example, the very thin-walled flat tubes and fins reach the brazing temperature more quickly than the header tubes and the additional tube, which have thicker walls. This can result in brazing defects which lead to leaks in the heat exchanger or which at least facilitate corrosive effects during the intended use of the heat exchanger.
Baffles which direct hot gas onto the components with a greater mass in order to accelerate the heating thereof and thus bring all the components to the brazing temperature simultaneously as far as possible have been installed in the brazing furnace in the prior art in order to solve the problems (e.g., U.S. Patent Application Publication No. US 2003/0111459A, inter alia). As regards such measures and similar measures, it may be mentioned as a disadvantage that there is a desire to braze products of different designs in the brazing furnace, requiring baffles matched to the different products and thereby giving rise to considerable expenditure.